General Clinical Reasoning and Integrated Case-Based Problems
Integrated cases test whether you can move from a presenting complaint to a prioritised differential, choose tests that change management, and act safely when the diagnosis is still uncertain.
Core rules
- Build illness scripts: age, onset, character, associated symptoms, risk factors. Compare and contrast competing diagnoses rather than reciting exhaustive lists.
- Pretest probability drives testing. A test shifts probability most when pretest probability is intermediate; high-sensitivity tests rule out (SnNout) and high-specificity tests rule in (SpPin).
- Rule out time-critical diagnoses first: acute coronary syndrome, aortic dissection, pulmonary embolism, ectopic pregnancy, meningitis, testicular torsion, necrotising enterocolitis.
- The response to treatment is diagnostic information; reassess when the course is atypical.
- Cognitive biases to name and counter: anchoring, premature closure, availability, confirmation bias.
Worked example
A 55-year-old smoker has 40 minutes of central chest pressure with diaphoresis and nausea. Reasoning: pretest probability of acute coronary syndrome is high, so obtain a 12-lead ECG within 10 minutes and serial high-sensitivity troponin; a single normal troponin at one hour does not exclude the diagnosis. Give aspirin and nitrates unless contraindicated. If the pain is tearing or there is a pulse deficit, consider aortic dissection before anticoagulation.
Traps
- Ordering tests that will not alter management.
- Accepting "gastritis" in a patient with cardiac risk factors.
- Discounting a compelling clinical picture because an early test was normal - as in early stroke or subarachnoid haemorrhage.
- Ignoring vital signs and trend data that contradict the working diagnosis.